<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body></body>
  <script>
    function reverseString(str) {
      let result = ''
      for (let i = str.length - 1; i >= 0; i--) {
        result += str[i]
      }
      return result
    }
    console.log(reverseString('hello')) // 'olleh'
  </script>
</html>